OK, this is just getting weird...

I had external interrupts working in the JAL prototype of my=20
remote-control receiver code, but I'm rewriting it in C18 (mainly=20
because I can do floating-point calculations for timer preload and=20
threshold values; JAL AIUI only handles integer math).

The thing is, I'm not seeing any interrupts -- none at all. I put a=20
breakpoint on the "goto ISR" line, and the PIC didn't break. I also=20
didn't see anything on the logic analyser....

I must be doing something stupid, but I can't for the life of me figure=20
out what:

#include <p18cxxx.h>
#pragma config OSC =3D HS     // High Speed Crystal oscillator
#pragma config WDT =3D OFF    // Watchdog timer off
#pragma config LVP =3D OFF    // Low-voltage programming off
#pragma config MCLRE =3D ON   // MCLR (reset) on
#pragma config FSCM =3D OFF   // Failsafe clock monitor off

// timer0 prescaler settings
#define TIMER0_USE_PRESCALER
#define TIMER0_PRESCALER_SETTING 5

// Infra-red receiver
#define PIN_IR                PORTBbits.RB0
#define PIN_IR_DIR            TRISBbits.TRISB0

void isr(void);

// ISR stub code
#pragma code HIGH_INTERRUPT_VECTOR =3D 0x8
void high_ISR (void)
{
     _asm
         goto isr
     _endasm
}
#pragma code

// Interrupt Service Routine
#pragma interrupt isr
void isr(void)
{
     unsigned char tval;
     char overflow;

     // Store timer value and overflow flag and rearm the timer
     tval =3D TMR0L;
     TMR0L =3D 0;
     overflow =3D INTCONbits.TMR0IF;
     INTCONbits.TMR0IF =3D 0;

     // detect RB0 int flag
     if (INTCONbits.INT0IF) {
         char pol;

         // clear interrupt flag
         INTCONbits.INT0IF =3D 0;

         // store bit polarity, then flip to other polarity
         pol =3D INTCON2bits.INTEDG0;
         INTCON2bits.INTEDG0 =3D !INTCON2bits.INTEDG0;
     }
}

void main(void)
{
     // Initialise pin directions
     LATA =3D LATB =3D 0;        // Clear port holding registers
     TRISA =3D TRISB =3D 0;        // Default to all outputs
     PIN_IR_DIR =3D 1;            // IR pin is an input

     // Set up timer 0
     T0CON =3D 0;            // Clear timer control register
#ifdef TIMER0_USE_PRESCALER
     T0CONbits.PSA =3D 1;        // Assign prescaler to timer0
     T0CONbits.T0PS0 =3D (TIMER0_PRESCALER_SETTING & 1)=3D=3D1;
     T0CONbits.T0PS1 =3D (TIMER0_PRESCALER_SETTING & 2)=3D=3D2;
     T0CONbits.T0PS2 =3D (TIMER0_PRESCALER_SETTING & 4)=3D=3D4;
#else
     T0CONbits.PSA =3D 0;        // Disable prescaler
#endif
     TMR0L =3D 0;            // Clear timer0 value

     // Set up interrupts
     INTCON2bits.INTEDG0 =3D IPOL_ACT;    // Trigger RB0 interrupt on
                     // active-going edge
     INTCONbits.INT0IF =3D 0;        // Clear RB0 interrupt flag
     INTCONbits.INT0IE =3D 1;        // Enable INT0 interrupt
     // The ISR handles the timer-0 overflow interrupt.
     INTCONbits.GIE =3D 1;        // Enable interrupts (globally)

     debug_word(0xCAFE);
     debug_word(0xBABE);

     for (;;) {
     }
}


Can anyone see what I'm doing wrong here? The chip seems to be acting as=20
if GIE were never set, but the SFR window suggests it *is* being set (as=20
is INT0IE)...

Thanks,
--=20
Phil.
piclist@philpem.me.uk
http://www.philpem.me.uk/
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